Everything HydroSewer does
Every capability below is available in the app today. All of them work without internet, except the optional map background.
Open .inp and .hydrosewer files
Import the EPA SWMM 5 file format and save your work in a native project format.
- Import EPA SWMM 5 .inp input files
- Open native .hydrosewer project files
- Parses all standard SWMM sections — [OPTIONS], [JUNCTIONS], [CONDUITS], [SUBCATCHMENTS], [POLYGONS] and more
- File-format validation with graceful handling of malformed files
- Save projects in the native .hydrosewer format, with Save project and Save as in the menu; the last saved project reopens when you open the app
- A .inp that declares a supported EPSG code in [TITLE] (Q_VAR_PROJECTION) lands on the map with no setup
- Demo Village, a sample network that shows on the map as soon as you turn it on
- Export the network, with your edits, as a standard SWMM .inp file (HydroSewer Pro)
The real SWMM 5 engine, on-device
The actual EPA SWMM 5 computational engine runs locally via FFI — no server, no cloud.
- Runs the real EPA SWMM 5 engine on your device
- Simulation runs in a background isolate, off the UI thread
- Pre-simulation validation checks for an outfall, links and isolated nodes before running
- Clear validation error messages when a network is not ready
- Check before running: manholes still at elevation 0 and depth 0, flat or uphill pipes, or a network with no inflow are pointed out first, with Run anyway or Cancel
- Progress indicators during execution
- Runs on iPhone, iPad and Android phones and tablets
Network editing & creation
Build and modify sanitary and storm sewer networks directly on the canvas.
- Edit node properties: invert elevation, max / initial / surcharge depth, ponded area, outfall type
- Node inflows: a sewage flow (DWF) in the network’s flow units, with an optional hourly pattern (24 multipliers) or one from the file, and a constant direct inflow — written to the .inp that is simulated and exported
- Edit link properties: conduit length, roughness, shape and diameter, plus pump, orifice, weir and outlet settings
- Edit subcatchment properties: area, width, slope, % impervious, roughness, depression storage and infiltration (Horton, Green-Ampt, Curve Number)
- Start a new network from the menu and add junctions, outfalls, storage units, conduits and pumps by tapping the canvas
- Lay out a preliminary network in the field: with the map on and Use my location, tap each manhole’s place on the map and it gets those coordinates. Not a substitute for a survey
- Move mode: drag nodes to reposition — connected links follow as you drag
- Delete mode with confirmation and cascade delete of connected links
- Renaming or deleting a node or link also updates the .inp data that names it (inflows, losses, vertices, controls), so the network still simulates
- Projects with references to elements that no longer exist are flagged when they open, with a Repair button
- Auto-generated IDs, duplicate checking and auto-calculated link length
- Live validation of ID uniqueness, node references and numeric input, with an unsaved-changes badge
Interactive network canvas
Zoom, pan and inspect every element — including subcatchments, unique to SWMM.
- Interactive canvas: zoom, pan and navigate the network
- Color-coded nodes (junction, outfall, storage, divider) and directional links (conduit, pump, orifice, weir, outlet)
- Subcatchment polygons for rainfall-runoff areas — unique to SWMM
- Semantic zoom keeps elements a constant visual size, with smooth repaint during gestures
- Fit-to-screen and zoom in / out controls
- Tap to select elements and see a quick properties card
- Live network statistics: element counts, bounds and zoom level
Simulation results
Read hydraulic results for every node, link and subcatchment across all timesteps.
- Node results: depth, head, volume, lateral inflow and flooding
- Link results: flow, velocity, depth and capacity
- Subcatchment results: runoff, infiltration and evaporation
- Every timestep saved as time-series data
- Mass-balance continuity error reporting
- Export node and link results to CSV, every time step, with units in the header (HydroSewer Pro)
Results visualization
Color-coded maps and a scrubbable timeline make results easy to read in the field.
- Nodes color-coded by depth: blue → green → orange → red
- Links color-coded by flow capacity
- Flooded and surcharging nodes highlighted
- Interactive timeline to scrub through simulation timesteps
- Color legend to interpret every result color
- Light and dark themes that follow your OS preference
Units, both systems
US Customary and Metric, detected from your model and applied everywhere.
- US Customary units (ft, ft², ft³/s, …)
- Metric / SI units (m, m², m³/s, …)
- Auto-detected from the FlowUnits in your .inp file
- Dynamic unit labels across the whole interface
Map background
See the network over Google Maps, find where it goes in one tap, and see where you are — optional, turned on by you, and the only feature that uses the internet.
- Google Maps under the network, as a map or satellite view, with adjustable map visibility
- Find your area on the map: tap your town and HydroSewer tries the coordinate systems it knows and proposes the one that fits, if any
- Use my location: the map centers where you are, and a dot shows your position as you walk. Your location never places or moves an element
- Or set the coordinates yourself: UTM, or in Advanced a Transverse Mercator grid (origin, false easting and northing, scale factor, meters or feet) or longitude/latitude
- Optional datum settings: ellipsoid and a 3-parameter shift to WGS84
- Network in local coordinates? Line it up by tapping a node and then its place on the map, 4–5 times
- Seeing the map and the line-up preview are free; saving the alignment is part of HydroSewer Pro
- No connection? The network is shown without the map, and everything else keeps working
- Available on iPhone, iPad and Android. Map: Google Maps
Core features without internet
Model, simulate, save and take notes with no connection. No account and no server behind the app.
- Open, edit and simulate a network with no connection — in the field, underground, anywhere
- Field notes, photos and saving work offline too
- Only the optional map background uses the internet, through Google Maps; purchases go through the App Store or Google Play
- Your GPS reading, if you allow it, is used on your device and never sent anywhere by HydroSewer; a note’s position leaves only in a project or PDF you share
- No account, no sign-in required
- No analytics or telemetry of HydroSewer’s own
- Your networks, models and results stay in local files on your device
Field notes & photos
Close the loop between the model and what is actually in the ground — free and unlimited.
- Notes on junctions, outfalls, storage, dividers and conduits, each Open or Resolved
- Photos from the camera or the gallery, with a zoomable full-screen viewer
- The same photo is stored once, and images are downscaled on import to keep the file small
- An amber ring marks every element that has notes — always visible on the canvas, not only in Notes Mode
- Notes Mode: tap an element and go straight to its notes
- One project-wide list of every open note, newest first, tap to jump to the element
- With location allowed, a new note records where it was taken and how accurately; Show on map takes you there, and the notes PDF includes it
- Notes and photos live in the .hydrosewer package and are never written to the .inp
Reports, export & saved projects
Hand your work on as files, and get back to yesterday’s project in one tap.
- Field notes PDF report: your logo, company and “Prepared by”, a summary and an index, a line of model data for each element, every note with its photos (two per row, with captions) and, when recorded, where it was taken with a View on map link
- Open notes by default; turn on Include resolved to add the resolved ones. US Letter or A4 by region, with the EPA/SWMM disclaimer
- Export the network as a standard SWMM .inp, and all results to CSV, every time step
- Share, print or save through the system sheet
- HydroSewer Pro, a one-time purchase, adds the notes PDF, the .inp and CSV export, and saving the map alignment; modeling, simulation, the map and field notes are free
- Saved Projects: reopen a recent project without the file picker
- Saving asks for a name and warns you before overwriting
In the works, not yet released
These are being built and are not available in the current release. We list them here so you know what's next — not as features you can use today.
Place a note by tapping the map
Drop an observation anywhere on the canvas, not only on an existing node or pipe. Designed, not yet implemented.
Field ↔ office sync
Stable element IDs and delete tombstones already make the format sync-ready, so a crew in the field and the office could share one project. There is no sync backend yet.
Sizing a pipe instead?
Sewer Pipe Calculator
The other half of the job: sizing. Diameter, slope, velocity and depth with Manning, and a gravity collector laid out segment by segment. No network model, no simulation engine.
Put your sewer models in your pocket
Available now on the App Store and Google Play — model sewer and stormwater networks with or without signal, wherever the work takes you.